The invention relates to a tensioning assembly for connecting an outer component having a cylindrical aperture to an inner component having a cylindrical outer surface and arranged concentrically in the aperture.
A first tensioning assembly of this type is known from German patent 23 29 940 A 1. Each individual conical ring disclosed therein has a conical surface and a cylindrical circumferential surface, the cylindrical circumferential surface resting directly against the opposite circumferential surface of the hub or shaft. A tensioning assembly in accordance with German patent 24 58 229 A 1, discloses conical rings having two conical circumferential surfaces wherein each conical ring is assigned a further conical ring which has a conical surface and a circumferential surface. The conical rings which interact with the tensioning screws thus exert their radial force on the adjacent cylindrical circumferential surface of the shaft or of the hub via the further conical rings.
The common feature of the two embodiments is that the conical rings and the circumferential webs of the double conical rings have the bores for the tensioning screws and the forcing screws on a common pitch circle and at the same spacings. As a consequence, at some locations on the circumference bores for forcing screws are arranged in the positions in which tensioning screws would normally be located. This design considerably simplifies the production on a drilling unit with corresponding dividing apparatus.
The uniform spacings, while providing advantages in terms of production, nevertheless involve problems regarding the correct installation of the front conical ring, the front conical ring being directed toward the caps of the tensioning screws. The problem of misalignment can occur whether assembly takes place at the factory or on site, e.g. when fastening belt-drive drums for conveying belts in mining or the like. Incorrect installation can easily occur because it is not easy to see, from the front, whether the conical ring is in the correct angular position with respect to the double conical ring. When in the correct position, the various types of bores coincide precisely. In the event of careless installation, sometimes the threaded bores in the front conical ring, (the front conical ring being directed toward the caps of the tensioning screws), and the threaded bores for releasing the front conical ring from the double conical ring, are located opposite and in alignment with threaded bores in the circumferential web of the double conical ring which are provided for the release of the conical ring directed away from the caps of the tensioning screws. Since the numbers of forcing screws for releasing the front conical ring and the rear conical ring are equal and the forcing screws are distributed uniformly over the circumference, all the threaded bores in the front conical ring may be located opposite the threaded bores in the circumferential web. No indication of this misalignment is given by insertion of the tensioning screws.
After the relative positions of the rings have been set, the forcing screws are screwed into the threaded bores of the front conical ring and come into contact with the threaded bores in the circumferential web. As a result, it is more difficult to force off the front conical ring because there is no real abutment to effect the necessary leverage. In addition, the threaded bores in the circumferential web are destroyed such that, in some circumstances, it is no longer possible to force off the rear conical ring and consequently the entire conical tensioning assembly can no longer be released.
It may be a number of years before this situation arises, when release of the tensioning assembly is already made difficult enough by corrosion and dirt. Accordingly, when such a case does occur, the damage is considerable.